The Old New Thing

Dragging a shell object, part 2: Enabling the Move operation

December 7, 2004 Dec 7, 2004 12/7/04

Raymond Chen

Let's say that we did want to support Move in our drag/drop program, for whatever reason. Let's do it with some scratch file instead of clock.avi, though. Create a file somewhere that you don't mind losing; let's say it's C:\throwaway.txt. Change the function OnLButtonDown as follows: void OnLButtonDown(HWND hwnd, BOOL fDoubleClick...

Dragging a shell object, part 1: Getting the IDataObject

December 6, 2004 Dec 6, 2004 12/6/04

Raymond Chen

The shell gives you the IDataObject; all you have to do is drag it around.

Why are documents printed out of order when you multiselect and choose “Print”?

December 3, 2004 Dec 3, 2004 12/3/04

Raymond Chen

If you select say five files and then right-click them and choose "Print", they tend to print in a random order. Why is that? The shell invokes the Print verb on each file in turn, and depending on how the program responsible for printing the document is registered, one of several things can happen. These three ways of registering ...

Why did Windows 95 run the timer at 55ms?

December 2, 2004 Dec 2, 2004 12/2/04

Raymond Chen

The story behind the 55ms timer tick rate goes all the way back to the original IBM PC BIOS. The original IBM PC used a 1.19MHz crystal, and 65536 cycles at 1.19MHz equals approximately 55ms. (More accurately, it was more like 1.19318MHz and 54.92ms.) But that just pushes the question to another level. Why 1.19...MHz, then? With that ...

What is the purpose of the bmPlanes member of the BITMAP structure?

December 1, 2004 Dec 1, 2004 12/1/04

Raymond Chen

Many bitmap-related structures in Windows have a field called "planes". For example the structure has a member (which must be set to 1). The structure has a field called . What's the deal with that field? The EGA video adapter supported 16 simultaneous colors. This was an enormous improvement over the CGA, which supported only four ...

What’s the difference between GetKeyState and GetAsyncKeyState?

November 30, 2004 Nov 30, 2004 11/30/04

Raymond Chen

I've seen some confusion over the difference between the function and the function. returns the virtual key state. In other words, reports the state of the keyboard based on the messages you have retrieved from your input queue. This is not the same as the physical keyboard state: When should you use and when should you use...

Why doesn’t the RunAs program accept a password on the command line?

November 29, 2004 Nov 29, 2004 11/29/04

Raymond Chen

The RunAs program demands that you type the password manually. Why doesn't it accept a password on the command line? This was a conscious decision. If it were possible to pass the password on the command line, people would start embedding passwords into batch files and logon scripts, which is laughably insecure. In other words, the ...

Simple things you can do with the ShellExecuteEx function

November 26, 2004 Nov 26, 2004 11/26/04

Raymond Chen

Here's a tiny little program: #include <windows.h> #include <shellapi.h> int __cdecl main(int argc, char **argv) { if (argc == 3) { SHELLEXECUTEINFO sei = { sizeof(sei) }; sei.fMask = SEE_MASK_FLAG_DDEWAIT; sei.nShow = SW_SHOWNORMAL; // added 27 Nov sei.lpVerb = argv[1]; sei.lpFile = argv[2]; ...

A sample of desktop icon text effects

November 25, 2004 Nov 25, 2004 11/25/04

Raymond Chen

So you can see what they look like.

Why can’t you drop directly onto a taskbar button?

November 24, 2004 Nov 24, 2004 11/24/04

Raymond Chen

If you drag a object and drop it onto a taskbar button, you get an error message that says, You cannot drop an item onto a button on the taskbar. However, if you drag the item over a button without releasing the mouse button, the window will open after a moment, allowing you to drop the item inside the window. Why doesn't the taskbar ...